A multidimensional selective landscape drives adaptive divergence between and within closely related Phlox species

Selection causes local adaptation across populations within species and simultaneously divergence between species. However, it is unclear if either the force of or the response to selection is similar across these scales. We show that natural selection drives divergence between closely related species in a pattern that is distinct from local adaptation within species. We use reciprocal transplant experiments across three species of Phlox wildflowers to characterize widespread adaptive divergence. Using provenance trials, we also find strong local adaptation between populations within a species. Comparing divergence and selection between these two scales of diversity we discover that one suite of traits predicts fitness differences between species and that an independent suite of traits predicts fitness variation within species. Selection drives divergence between species, contributing to speciation, while simultaneously favoring extensive diversity that is maintained across populations within a species. Our work demonstrates how the selection landscape is complex and multidimensional.


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Behavioural & social sciences study design All studies must disclose on these points even when the disclosure is negative.The data include measurements of leaves, flowers, fruits, survival across three years in natural environmental conditions.All individuals were randomized in location within each gardens.
The plants included in this study include 122 individuals of Phlox amoena (from 8 populations), 125 individuals of Phlox pilosa (from 9 populations), and 37 genotypes of Phlox pilosa deamii (from 3 populations).These populations are sampled from the across the ranges of these three species and the diversity includes the known diversity of these species.
Ten to twenty individuals from populations across the species ranges were chosen to be included in this experiment.The number of populations used were limited by availability of found populations, the number of individuals per population was limited by ability and availability of propagating individuals in the greenhouse.Total sample size was limited by human feasibility and space limitations.
Data were collected by the authors over the course of three field seasons.All data were collected with pencil and paper and entered into electronic data files.Data were collected without knowledge of species identity or population source at time of collection.
We included all available and verifiable data in our analyses.
This experiment was performed one time across three spatial replicates and over a period of three years.It was not replicated in its entirety.We repeated measurements of leaf traits on plants grown in the field and in the greenhouse to verify that the differences between species were robust and reproducible across environments.
Experimental plants were labeled with anonymous numbers and data was collected by number without knowledge of the plant species or source location.
The field work took place over three years with variable conditions and weather.
The garden sites were minimally disturbed with plantings and all plants and materials were removed at end of experiment.Fruits and seeds were collected to the best of our abilities as plants matured.All samples included in this study were collected with permits from the US forest service (USDA #005277 05/2017) and the South Carolina Department of Natural resources (SCDNR SU-12-2017 04/2017) and/or with permission from private property owners.The use of the land at Land Between the Lakes was used in accordance with permit #LBL17170.
Common gardens that were approximately 25X25 meters were planted in April 2018 and data collection was completed in September 2020.Data was collected at non-regular time intervals throughout the growing season of 2018 and 2019.Visits to the field sites in 2020 was limited due to the COVID pandemic.We were only able to collect final survival in September of 2020.
All gardens included clonal replicates of the same individuals and all individuals were randomly positions across blocks at each garden site.Each block contained the same number of individuals from each species but in a different randomized order.
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